In particular,
VSG = 0.35 V so the gate potential is 0.65 V. Figure 20.10b shows how the reference and
output currents vary if VDD is swept from 900 mV to 1 V. The reference current is
linearly dependent on VDD (as seen in Ex. 20.1). The output current is dependent on both
the reference current and the VDS (A.) of M2. In general, we want a reference current that
isn't dependent on power supply or ground variations (noise). This is an important point.
Consider the following example.